Abstract:
Mango anthracnose caused by Colletotrichum gloeosporioides is among the most
important diseases of fruits in subtropical and tropical regions of the world. Currently, the
control of fruit and vegetable diseases relies mainly on the use of synthetic fungicides.
However, due to peoples‘ concern on the side effects of synthetic fungicides, looking for
non-chemical control methods to reduce postharvest decay is becoming crucial. The aim of
this study was therefore, to isolate and characterize Colletotrichum spp., screening and
evaluation of potential microbial antagonists against Colletotrichum gloeosporioides; and
those potential antagonistic isolates viz Lactobacillus and yeast isolates were evaluated
tolerant for reidomil and mancozab fungicide. Isolationof Colletotrichum spp. was done
from symptomatic anthracnose infected mango fruits and a total of 72 isolates were
screened from the host. Based on phenotypic characteristics, the isolates were divided in to
six distinct morphotypes. Based on morphological, physiological and cultural
characteristics, four were found to be C. gloeosporioides, while the remaining two were
found to be C. acutatum. Secondly, potential antagonistic microbes were isolated and
characterized from healthy looking mango fruits against C. gloeosporioides. A total of 66
yeast isolates and 48 Lactobacillus isolates were screened out of which 16 yeasts and seven
Lactobacillus isolates were found to be effective in inhibiting the growth of C.
gloeosporioides pathogen on dual culture and over lay dual culture methods respectively.
Based on microscopic and macroscopic characterizations and other morphological,
cultural, biochemical and physiological tests, the yeasts were characterized to be Candida,
Cryptococcus, Saccharomyces, and Rhodotorula and the Lactobacillus isolates were
characterized to be Lactobacillus acidophilus. In vitro and in vivo results of this study
revealed that the antagonists (yeast and Lactobacillus) inhibited mycelial growth of the
pathogen (C. gloeosporioides) as compared to the control in the dual culture assay. The
mechanism of the antagonists to inhibit the growth of the pathogen revealed that
antagonistic Lactobacillus and yeast isolates were able to produce antifungal compounds.
In vivo experiments of these antagonists were also tested against the pathogen (C.
gloeosporioides) and the results of this study indicated that both Lactobacillus and yeast
antagonist isolates were able to inhibit the pathogen. The third objective of this study was
to evaluate the fungicide tolerance of potential antagonistic isolates viz Lactobacillus and
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yeast isolates. The fungicide tolerance of potential antagonistic isolates viz Lactobacillus
and yeast isolates revealed that all yeast isolates were tolerant to both fungicides at the
highest concentration (2000ppm). It was however, observed that the percentage inhibition
increased as the concentration of the fungicide was increased. Similarly, Lactobacillus
isolates were found to be tolerant to both fungicides under all concentration treatments.
Therefore, the results of the study imply that these antagonists could be used to control
mango anthracnose disease integrated with low dosage of these fungicides as part of
integrated management of mango anthracnose disease. This study contributes a novel
report on the biocontrol of mango anthracnose disease by the application of possibly new
antagonist Lactobacillus and yeast isolates. Thus, the use of a combination of biological
control agents with commercial fungicides as a safe and effective disease management
option against the post harvest anthracnose of mango fruits could be recommended